Bacillus thuringiensis (B.t.) produces an insect toxin designated as .delta.-endotoxin. It is synthesized by the B.t. sporulating cell. The toxin, upon being ingested in its crystalline form by susceptible insects, is transformed into biologically active moieties by the insect gut juice proteases. The primary target is insect cells of the gut epithelium, which are rapidly destroyed.
The reported activity spectrum of B.t. covers insect species within the order Lepidoptera, many of which are major pests in agriculture and forestry. The activity spectrum also includes the insect order Diptera, which includes mosquitos and black flies. See Couch, T. L. (1980) "Mosquito Pathogenicity of Bacillus thuringiensis var. israelensis," Developments in Industrial Microbiology 22: 61-76; Beegle, C. C., (1978) "Use of Entomogenous Bacteria in Agroecosystems," Developments in Industrial Microbiology 20: 97-104. Krieg, et al., Z. ang. Ent. (1983) 96: 500-508, describe a B.t. isolate named Bacillus thuringiensis var. tenebrionis, which is reportedly active against two beetles in the order Coleoptera. These are the Colorado potato beetle, Leptinotarsa decemlineata, and Agelastica alni. In European Patent Application No. 0 202 739 there is disclosed a novel B.t. isolate active against Coleoptera. It is known as B. thuringiensis var. san diego (B.t.sd.). U.S. Pat. No. 4,966,765 discloses the coleopteran-active Bacillus thuringiensis isolate B.t. PS86B1.
Ants comprise a large group of insects (Family Formicidae) from the taxonomic order, Hymenoptera. They are among the most common house pests. In many situations, ants are a nuisance pest. Foraging ants create problems with hygiene in hospitals and the food industry. Ants also create problems in agriculture. Damage can be caused by direct feeding on plants. Harvester and fire ants are commonly associated with this type of damage (Holldobler, B. and Wilson, E. O. 1990. The Ants, Belkap Press, Cambridge, Mass. 732p.). Some ants cause indirect damage by nurturing and protecting sap feeding insects such as mealybugs and aphids. Ants, particularly in the genus Solenopsis are capable of producing extremely painful stings to humans. It has been estimated that approximately 10,000 stings occur each year (Habermehl, G. G. 1981, Venomous Animals and Their Toxins, Springer-Verlag, New York, 195 p.). The Pharoah ant (Monomorium pharoanis) is primarily an urban pest. However, this species can also be an agricultural pest and damage to corn has been noted (Ebeling, W. 1978. Urban Entomology, UC Press, Berkely, Calif., 695p.).